Rotary valves of the ball valve or plug valve type are used as gas stops and for certain other purposes. It is desirable to construct gas stops so that they cannot be disassembled and reassembled by any unauthorized person. Many arrangements have been developed to make tamperproof valves of the character described. For instance, U.S. Pat. Nos. 2,539,106 to Schenck, dated Jan. 23, 1951; 2,989,081 to Johnson, dated Aug. 4, 1954; and 3,359,999 to Mueller, dated Dec. 26, 1967; all show one form or another of a valve actuator element which is readily assembled and difficult if not prevented from being disassembled. This is accomplished by a snap ring or spring which is inwardly retractable into a groove in the actuator element during assembly and which is outwardly expandable into a locking groove in the valve body when fully assembled. A problem with such constructions is that the snap rings or springs tend to ride out of the locking groove after extended use and wear. Consequently, more positive constructions were developed as shown in Poisker U.S. Pat. No. 3,004,550, dated Oct. 17, 1961.
Most tamperproof gas stops, such as that shown in the Poisker patent, were developed to rely upon the use of some sort of locking arrangement that requires a special tool to release the valve plug for removal from the valve body. In most such instances, the expedience used to make the ball or plug valve tamperproof added substantially to its cost.
Accordingly, an improved tamperproof plug valve was developed as disclosed in U.S. Pat. No. 4,014,512 to Cheever et al, dated Mar. 29, 1977 and assigned to the assignee of this invention. That patent shows a tamperproof plug valve which requires no special parts other than the valve body and the valve plug. After the valve plug is inserted into the valve body, two stacked, slit, frusto-conical, transversely arched spring washers having teeth make a one-way tight friction fit on a projecting end portion of the valve plug. The outer peripheral portion of the forward of the two washers bears on a recessed planar area of the valve body which is surrounded by a continuous boss so a prying tool cannot be inserted beneath either washer.
The instant invention provides a rotary valve, shown as a ball valve, wherein the basic means of an expandable locking ring is used for rendering the valve tamperproof but means are provided for preventing the locking ring from riding out of its locking groove should removal of the actuator be attempted.